No thats not crazy, I might have spread it out to like 10 - 20 seeds a pot, your gonna have a hell of a time transplanting later. I would transplant the seeds into their own little pot (I use empty 16oz water bottles cut in half with holes cut in the bottoms for a cheap alternative to buying 50-60 starter pots) as soon as they sprout so as to avoid tangled roots, and transplant shock.
As for the age of the seed, pot seed can be kept indefinably if stored properly. In fact, Paul Gould, owner of Barney's coffee shop in Amsterdam (tied at 34 with their only real competition Green House Seeds for the title of most cannabis cup winners) is bringing out an over 20 year old seed from a master strain of the fabled Acapulco Gold, to the 2010 Cannabis Cup! You know what that means!! New strains, YAY!